The best litter-picking kit is the one you barely notice you are carrying. A folded bag in a coat pocket, a pair of gloves in the boot of the car, ten spare minutes on a familiar riverside path. That is enough to make a visible difference to a stream, week after week, without waiting for an organised clean-up that happens twice a year at best.

Start with a single bag, not a big clean-up

Litter arrives daily. A crisp packet blows off a picnic bench on Tuesday, a raft of wet wipes gathers behind a fallen branch on Friday, and after heavy rain the whole lot is rearranged. Small, frequent effort beats occasional heroics, because it catches rubbish before it breaks into fragments that no one can ever remove.

The trick is to work the strandline — the line of debris left along the bank a metre or so above the water after a spate. That is where the river parks what it has carried downstream, and it concentrates your effort. Ten minutes on a strandline will clear more than an hour of wandering about at random.

• A sturdy reusable sack, with handles wide enough for gloves
• Gardening gloves, or nitrile-coated ones that grip wet plastic
• A litter picker for anything you cannot identify by sight
• Alcohol hand gel, and a few waterproof plasters
• A small rigid tub with a lid, for anything sharp
• Your phone, for photographs and for reporting problems

How to pick up safely

Riverbank litter is dirtier than pavement litter, and the water carries bacteria that can make you properly ill. Leptospirosis, sometimes called Weil's disease, is the one to respect: it spreads through water contaminated by rodent urine. Cover any cut with a waterproof plaster before you start, keep your hands away from your face, and wash or gel them as soon as you finish. If you feel flu-like symptoms a week or two after a riverside walk, mention the walk to your GP.

Never reach into undercut banks, silty water, or anything you cannot see into. Broken glass, discarded fishing hooks and needles all end up there. Use the picker, put sharps in the rigid tub, and if you are at all unsure, leave the item exactly where it is and report the location instead.

Avoid steep, muddy or fast-flowing banks on your own, and tell someone where you are going. Before you begin, look at what you are about to disturb: gravel bars may hold nesting waders, and a heap of dead leaves by a wall could be a hedgehog. Lift nothing unnecessarily, and leave stones where they lie, since everything under them is somebody's home.

What to take, and what to leave behind

Most of what you find is straightforward: drinks bottles and cans, crisp packets, sweet wrappers, cigarette butts, plastic bags, balloon ribbons, expanded polystyrene, wet wipes and sanitary items (which never break down, whatever the packet claims), and tangles of discarded fishing line, which maim swans and moorhens. Take it all, and recycle the clean bottles and cans at home.

But a riverbank is not a tidy garden, and some things belong there:

• Woody debris, fallen branches and leaf litter — these shelter invertebrates and fish fry
• Gravel, stones and silt, which should never be raked or dredged by hand
• Dead fish, unless you find several together, which is worth reporting
• An oily sheen or a strange discolouration on the water, which needs reporting rather than mopping
• Fly-tipped tyres, fridges and shopping trolleys — note the exact spot and tell the landowner, your local council or the environmental regulator

Slow down and watch: the walk as a nature journal

Picking up litter is a wonderful excuse for a slow walk, because you are already looking at the ground. Keep half your attention on the water. A flash of electric blue low over the surface is a kingfisher; a brown bird bobbing on a midstream stone is a dipper; a grey wagtail will often work the shallows ahead of you. Look for the burrows of water voles in soft banks, and for otter spraint on flat stones — it smells faintly of fish, and there is no need to get any closer than that.

Write it down when you get home. A few lines is plenty:

• Date, time and weather, plus the height and colour of the water
• What you saw or heard, and anything new for the season
• How much litter you collected, and anything unusual
• Anything you reported, and to whom

Within a year you will have a record of your stream's own rhythm: the week the mayflies hatch, the first frost that clears the weed, the warm weekends that leave a scatter of canisters and bottles behind. That kind of noticing is what turns a walk into a relationship.

Share the clean stretch

Take a photograph of the same bend before and after you work. A picture of a clean bank is quietly persuasive; it says this is what normal looks like here, and it makes the next person think twice about dropping a wrapper. Post it in a local group, thank the people who already look after the stretch, and keep the location vague if the spot holds otters, nesting birds or rare plants.

Leave the stream better than you found it — that is the whole method. Carry one bag, fill it, take it home, and do the same next week. Encourage the people you meet, too: anglers, paddlers and dog walkers all care about the same water, and most will happily pocket a bottle or two on their way past. If a spot is beyond one bag, report it rather than struggling; that needs a phone call, not a bigger sack.

Do this often enough and the reward stops being the rubbish you remove. It becomes the heron that no longer has to pick its way through plastic, the clear gravel where the dace spawn, and a notebook slowly filling with the seasons of one small, well-loved stream.